The present invention relates generally to cooling systems for electrical machinery and more particularly to a rotating heat pipe rotor structure for cooling rotors in electric generators, motors or the like.
Electrical systems in military and commercial aircraft typically include electrical power generators having permanent magnet rotors which generate heat during operation as a result of eddy current and hysteresis losses. Because the temperature difference between the core of the rotor and its peripheral surfaces may be large (about 150.degree. C.), rotor cooling may be required to attain a desirable level of operating efficiency.
Existing cooling methods include convective air or oil circulation through a passageway defined through the rotor shaft. Bleed air from the aircraft engine compressor is not effective as coolant because of poor heat transfer and low heat capacity associated with air, and use of bleed air may reduce overall engine performance. Oil circulation causes viscous frictional loss for the rotor which reduces overall efficiency. Oil jet cooling is not efficient because of poor thermal contact between the drive shaft and rotor.
The invention solves or substantially reduces in critical importance problems with prior art rotor cooling structures by providing a rotor structure comprising a rotatable heat pipe having a plurality of fins defining radially extending vapor chambers in the evaporator end of the heat pipe for absorbing waste heat from the rotor core by vaporization of the heat pipe working fluid and removing heat at a heat exchanger in thermal contact with the condenser end of the heat pipe. The finned multi-chamber evaporator structure of the invention provides substantially improved and uniform cooling of the rotor core as compared to prior art structures. Problems with high differential temperatures and thermal stress within the rotor core are substantially eliminated.
Efficient rotor cooling may prevent overheating and premature failure, and thus may improve reliability and maintainability, of the electrical generators or motors incorporating the invention. Use of the invention on an aircraft may result in overall weight reduction of aircraft systems. Utility of the invention may also be found in ground based electrical machinery such as ground carts, portable generators, environmental control equipment and lightweight motors for electrical transportation.
It is therefore a principal object of the invention to provide a structure for cooling rotors in high power electric generators, motors or the like.
It is another object of the invention to provide a structure for cooling rotors in electric generators, motors or the like utilizing a rotatable heat pipe structure.
It is another object of the invention to provide a rotatable heat pipe structure for cooling rotors in electrical equipment aboard aircraft.
It is a further object of the invention to provide a rotatable heat pipe structure for cooling rotors in electrical machinery to improve power density or power-to-weight ratio thereof.
It is a further object of the invention to provide a rotor structure for low temperature operating electrical machinery.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.